Page 21 - Gi flipbook May 2018

CO The symptoms of exposure to low levels
is a colourless,
odourless gas
of CO can be similar to those of many
which causes
asphyxiation
through
and flu. The most common symptoms
hypoxia. When inhaled, it combines other conditions, such as food poisoning
with the oxygen in the red blood cells
to form carboxyhemoglobin. As the include headache, nausea, dizziness,
concentration levels of CO increase,
it prevents the bloodstream’s tiredness and confusion, stomach pain
remaining oxyhaemoglobin from and shortness of breath
transferring oxygen to important
tissues, thus killing the living cells.
As CO affects one’s cognitive
abilities, it can incapacitate the victim insufficiently audible, or if the non-volatile memory after
without their knowledge. Any sudden occupants are infirm, pregnant, commissioning to enable better
exertion can cause collapse and, children, heavy sleepers, intoxicated, discrimination. This circuit was also
as a result, evacuation of the area or have a hearing impairment. capable of allowing for drift due to
becomes impracticable. The temperature or age of the
symptoms of exposure to low levels BRIDGING THE GAP piezoelectric speaker and battery
of CO can be similar to those of many To create viable, isolated scenarios for within the CO detector.
other conditions, such as food research and development, the siting After packaging the second revision,
poisoning and flu. The most common requirements for the alarms in further tests were conducted and it
symptoms include headache, nausea, accordance with BS EN 50292 were was found that ringing caused by
dizziness, tiredness and confusion, considered. multipath reflections and pulse
stomach pain and shortness of breath. Based on these requirements, a stretching, or narrowing caused by
It is currently advisable to mount means of detecting the CO alarm excessive reverberation were leading
domestic CO detectors at ceiling effectively over a short range can be to an increase in reaction time. To
level, away from dead spaces or achieved through the use of a overcome this, the software was
obstructions, for effective detection. specially designed circuit comprising a revised to counter the distortion and a
A compromise is normally necessary microphone. The design was also means of mechanical noise
between CO detectors being sited focused around the most commonly attenuation was designed to act as a
near potential sources of CO gas and available types of CO detector that filter to free up the processing power.
the alarm being loud enough to be are approved to BS EN 50291 Type B,
heard throughout the building. Such which are capable of generating a QUALITY, SIMPLICITY
detectors are mainly battery distinctive sound pattern. AND SUSTAINABILITY
powered, enabling a simple low cost A basic alarm detection circuit was The device is installed in between the
installation and usually do not created using minimum viable appliance and electrical supply. In
require battery replacement during resources to conduct further testing most instances this can be achieved
their operational life. where basic alarm characteristics by removing the supply cable from a
When an integrated response level were monitored. typical outlet, such as a switched
is exceeded, the CO detector is While this design allowed for the fused spur, and installing it into the
operable to output an audible alarm, responsiveness to be altered, it power output of the CO interlock. A
which, at best, would alert the became evident from initial field tests new supply can then be installed from
occupant to take action in the form of that the prototype was vulnerable to the switched fused spur to the power
manual isolation of power to an sustained noise. input of the CO interlock.
electrically controlled appliance. Such In order to improve the In order to avoid false alarms, the
intervention is likely to expose the discrimination of the sensor circuit, CO interlock works by monitoring the
responsible person to a greater level the introduction of a microcontroller audio alarm characteristics of
of CO gas. By this time, the occupant and software capable of sampling, commonly used CO detectors. If the
may already be suffering from the storing and referencing the key alarm alarm is considered valid, then the
symptoms of low exposure, such as characteristics from other noise interlock disconnects the electrical
dizziness and confusion. Entering a sources was required. However, mains supply to an associated fuel
room in which the defective appliance applying this to the current hardware burning appliance. The interlock is
is located can elevate the symptoms, design was not practical and further usually close to the appliance and the
ultimately leading to unconsciousness, revisions were required which called CO detector must be appropriately
brain damage or death. If no isolation for more research and development located in the same area to provide
of the appliance can be safely into electronics and software. adequate protection, as required by
achieved, the appliance may continue To give the microcontroller a very BS EN 50292. It may also be possible
to operate and raise the concentration high false alarm immunity, a new that other interlinked CO detectors
of CO, which is capable of affecting analogue alarm detection circuit was could be used in other areas away
life in adjacent properties. This could designed to lock itself to the from the protected area, for example
occur when the building is particular alarm characteristics and in bedrooms.
unoccupied, if the alarm is compare it to a copy stored in In consideration of the environment,

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